of course it is, are there any doubts?
actually the best translation of the suffix is con-:
soutok – sútok – sutok – confluence
soused – sused (arch. súsed) – suśed – neighbour, literally: consettler
souvaha – súvaha – suvaha – balance (in accounting), literally: conweight
hungarian has preserved some of these suffixes in archaic, nasalized forms, e. g. somszéd [somseid, somsiid] – neighbour
p.s. ou is a diphtong, not a single vowel

oh what the hell…
its szomszéd, not somszéd, prefix, not suffix and diphthong, not diphtong. i must have been drunk when i wrote this :D